FIG. 1 illustrates an N-level current steering DAC 100 according to the prior art. The DAC 100 includes a reference arm and a set of current elements (five current elements 110,115, 120, 125 and 130). The reference arm includes a reference amplifier 105 receiving a reference voltage and a feedback voltage, a reference resistor 135 and a reference element, for example current element 110.
Conventional DAC architectures as shown in FIG. 1 apply dynamic element matching (DEM) algorithms to whiten and reduce noise (especially flicker noise in low frequency applications) from the current elements of the DAC. In spite of the noise reduction from the current elements, output noise of the DAC is dominated by the noise from the reference arm and the reference amplifier 105, both used for generating a reference current needed for the DAC. While steering current, the noise (current noise) from the reference arm gets multiplied by a mirroring ratio of the DAC and appears at the output of the DAC. The current noise includes both thermal and flicker noise of the current elements of the DAC. To reduce the current noise, the reference current needs to be significantly increased which results in increased power consumption. Also, resistance of the reference resistor 135 needs to be reduced in order to increase the reference current. This results in increasing the current noise contribution of the reference resistor 135. The reference amplifier 105 is typically a differential-to-single-ended amplifier that can be chopped for noise reduction. However, reference resistor 135 and the reference element noise become the bottleneck in reducing output current noise of the DAC.